message: unable to log in to the user account user at this time

Friday, when I tried to enter my computer I have received a log screen. Tried to log but I have received this message you are unable to log in to the user account user at this time because an error occured (never happened before). I am sure that the passowrd is correct because the screen doesnt shake, like it happens when I introduce a wrong passord.
Tried to reboot with "apple S" pressed to go to the root. When I acces the directory "Users" I cannot see my user name anymore. Filevault is not activated, never did it.
I have very important data from work (my whole year work), I dont have backup and I must not loos it.
I was not trying to do an updade or anything, it just happen when I turn on the Mac.

I have tried to do the following things too:
First thing:
Boot from installation disk #1:Accessed Disk Utility and repaired the disk. There was one error "Mounting of the drive" that was fixed. No other errors found. When i rebooted i got the same message at the login screen.

Tried to change the password. I got an error telling me that i don't have permission or an error has occurred.

Did the fsck -fy:
The volume Macintosh HD appears to be ok
rebooted and still had the same problem.

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